The Skeletal System 169
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Figure 7- 25
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David
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Dr.^ by (^)
Photography
Cincinnati
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®^
Learning^ of^
Cengage(^) University (^)
Fankhauser,
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2016
©^ (D)^
(C) Lateral view of the bones of the foot; superior view of the bones of the foot. (Continued)
David
Dr. by
PhotographyCincinnati.
® Learningof CengageUniversity 2016Fankhauser, ©
The Arches of the Foot
The bones of the foot are arranged in a series of arches that
enable the foot to bear weight while standing and to
provide leverage while walking. There are two longitudinal
arches and one transverse arch. The medial longitudinal
arch is formed by the calcaneus, talus, navicular, the three
cuneiforms, and the three medial metatarsals. This is the
highest arch
of the foot and can easily be noted. The lateral longi-
tudinal arch is much lower and is formed by the cal-
caneus, the cuboid, and the two lateral metatarsals. The
transverse arch is perpendicular to the longitudi-nal arches
and is most pronounced at the base of the metatarsals.
The term pes planus, or flatfoot, indicates a de-creased
height of the longitudinal arches. It rarely causes any pain.
As The Body Ages
As we age, less protein matrix is formed in our bone tissue accompanied by a loss
of calcium salts. Bones become more fragile and tend to break more eas-ily in
older adults. Older adults also develop stiffness and less flexibility of the skeleton
due to a decrease in the protein collagen found in the tendon connec-tive tissue
that connects bone to muscle, and in ligaments that connect bone to bone. Hence,
as we age we should be more conscious of our diet and include more foods that
contain calcium. Regular exercise can also help maintain healthy bone tissues.
Walking is an excellent way to exercise both bones and muscles.^
Do we really “shrink” as we grow older? Shrinking is caused by a thinning of the inter-
vertebral disks in the spinal column. Starting at around age 40, individuals can lose about one-
half inch in height every 20 years due to the loss of disk protein.